RFR: 8352185: Shenandoah: Invalid logic for remembered set verification [v13]

[Xiaolong Peng]

On Fri, 21 Mar 2025 04:00:17 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> I'll add comment here as you are suggesting.
>
> I was suggesting looking to see if normal perf measures showed any improvements. E.g. if you ran say SPECjbb and compared the remset scan times for the minor GC's that followed global collections.

I have run h2 benchmark, here is the remembered set scan times after a global GC, it does seem to improve  remembered set scan time in this case:

PR version:

[2025-03-21T07:35:41.801+0000][10.292s][19715][info ][gc             ] GC(6) Concurrent remembered set scanning 13.069ms
[2025-03-21T07:35:48.088+0000][16.579s][19715][info ][gc             ] GC(9) Concurrent remembered set scanning 5.537ms
[2025-03-21T07:35:56.610+0000][25.101s][19715][info ][gc             ] GC(14) Concurrent remembered set scanning 6.186ms
[2025-03-21T07:36:03.967+0000][32.459s][19715][info ][gc             ] GC(18) Concurrent remembered set scanning 9.562ms
[2025-03-21T07:36:11.234+0000][39.725s][19715][info ][gc             ] GC(22) Concurrent remembered set scanning 2.591ms
[2025-03-21T07:36:17.303+0000][45.794s][19715][info ][gc             ] GC(25) Concurrent remembered set scanning 0.999ms
[2025-03-21T07:36:25.647+0000][54.139s][19715][info ][gc             ] GC(30) Concurrent remembered set scanning 1.665ms
[2025-03-21T07:36:32.790+0000][61.281s][19715][info ][gc             ] GC(33) Concurrent remembered set scanning 2.851ms
[2025-03-21T07:36:40.241+0000][68.732s][19715][info ][gc             ] GC(36) Concurrent remembered set scanning 0.716ms
[2025-03-21T07:36:47.440+0000][75.931s][19715][info ][gc             ] GC(39) Concurrent remembered set scanning 1.932ms


master:

[2025-03-21T07:34:04.978+0000][10.765s][17923][info ][gc             ] GC(6) Concurrent remembered set scanning 22.813ms
[2025-03-21T07:34:11.250+0000][17.038s][17923][info ][gc             ] GC(9) Concurrent remembered set scanning 14.457ms
[2025-03-21T07:34:18.692+0000][24.480s][17923][info ][gc             ] GC(14) Concurrent remembered set scanning 4.972ms
[2025-03-21T07:34:26.033+0000][31.820s][17923][info ][gc             ] GC(18) Concurrent remembered set scanning 9.134ms
[2025-03-21T07:34:34.416+0000][40.203s][17923][info ][gc             ] GC(22) Concurrent remembered set scanning 3.655ms
[2025-03-21T07:34:42.180+0000][47.967s][17923][info ][gc             ] GC(26) Concurrent remembered set scanning 3.253ms
[2025-03-21T07:34:49.371+0000][55.168s][17923][info ][gc             ] GC(29) Concurrent remembered set scanning 1.615ms
[2025-03-21T07:34:56.592+0000][62.396s][17923][info ][gc             ] GC(32) Concurrent remembered set scanning 1.570ms
[2025-03-21T07:35:03.766+0000][69.575s][17923][info ][gc             ] GC(35) Concurrent remembered set scanning 1.040ms
[2025-03-21T07:35:10.941+0000][76.753s][17923][info ][gc             ] GC(38) Concurrent remembered set scanning 1.947ms

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PR Review Comment: https://git.openjdk.org/jdk/pull/24092#discussion_r2007788818